Telephone-exchange system.



R. E. NOBLE.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED NOV- 6,1916- Patented May 21,1918.

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ROY E. NOBLE, OF NEW YORK, N. Y., ASSIG-NOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented May 21, 1918.

Application filed November 6, 1916. Serial No. 129,731.

To all whom it may concern:

Be it known that 1, Box E. NOBLE, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to private branch exchange systems.

Under usual conditions prevalent in private branch exchange systems, the number of the many extension telephone lines terminating a private branch switchboard which, durin the periods when no operator is at the switclfiaoard, can be connected to make outgoing calls over the trunk circuit extending to a central oflice, is limited to the number of trunk circuits extending from the private branch exchange to the central ofiice.

The object of the present invention is the provision of means whereby, without increasing the "number of trunk circuits, each and every one of the stations on extension telephone lines terminating at a private branch exchange may make outgoing calls during the period when no operator 1s at the private branch exchange.

In accordance with the present invention, there are provided switches through which the extension lines normally extend to the usual terminals on the switchboard of the hen I these switches are actuated, the extension lines are then connected to terminals on a line finding switch located at the private branch exchange. A call being initiated at any of the extension telephone stations sets the finder switch in operation to find the calling line and, when found, the apparatus functions to connect it with the trunk circuit.

For a more complete [understanding of this invention, reference should be had to the following description, taken in connection with the accompanying drawing, in which there is shown a trunk circuit A extending from .a central office and terminating at a switchboard of a private branch exchange. There are .also shown extension lines B and C terminating at the private branch exchange, and a cord circuit D ordinarily employed forcompleting connections between the extension lines and the trunk circuit. In each extension line there is a key 5, through normal contacts of which the extension line leads to a jack 6. Also located at the private branch exchange is a line finding switch E, provided with a ratchet wheel 10, mounted on a suitable shaft 11 which carries an arm 12 supporting brushes13, let, 15 and 16. A holding pawl 17 and a stepping pawl 18 normally engage the ratchet wheel. The stepping pawl 18 is controlled by a stepping magnet 19. The line finding switch is also provided with a contact ring 20 which is grounded. The brush 16, in its normal position, is out of engagement with the ring 20, but when the ratchet wheel has been moved one step from its normal position, brush 16 engages ring 20 and remains in engagement therewith until the switch again reaches its normal position. The line finding switch E is provided with a plurality of sets of stationary terminals, there being a set for each extension line.

In the normal operation of private branch exchange systems, when an operator is .at the switchboard, calls on the extension lines are received by the operator and connection is made between a calling extension line and the trunk circuit by means of the cord circuit D. However, when the switchboard is to be left withoutan attendant,the attendant before leaving, actuates the keys 5 to disconnect .the extension lines from the jacks, and to connect them with the terminals of the line finding switch E.

Assuming under such conditions that the subscriber on extension B should now desire to make an outgoing call, the removal of the receiver from the switchhook causes the operation of a starting relay .30, which is common to all the extension lines, and, in

.hand armature to cause stepping pawl 18 to advance the ratchet wheel one step. The operation of stepping magnet 19 also attracts its left-hand armature, closing a short-circuiting path for the winding of the stepping magnet so that as soon as it is operated it releases. Upon the first advancement of the ratchet wheel, thebrushes 13, 14 and 15 are brought into engagement with the terminals associated with one of the extension lines C, but since the test terminal thereof is not connected to battery, the switch does not stop on those terminals. On the first one-step advancement of the ratchet wheel from normal position, the brush 16 engages contact ring 20, whereupon a circuit for relay 32' is completed. Relay 32 thereupon operates, connecting battery in circuit with its winding, whereupon relay 32 will be maintained operated independent of the contact of starting relay 30. Since stepping magnet 19, upon operating, short-circuits itself, it releases,

whereupon the stepping pawl, due to the,

action of the spring 33, drops back to engage the next tooth of the ratchet wheel,

and stepping magnet is again energized to advance the ratchet wheel another step. Assuming that the set of terminals connected with extension line B is the second set from the normal position of the switch, the second advancement of the ratchet wheel will bring the brushes 13, 14 and 15 into engagement with the terminals of the extension line B, whereupon relay 34 operates over a circuit from battery, through the contact of relay 31, test terminal and brush 15 of the switch E, and the winding of relay 34 to ground. The operation of relay 34 opens a contact in the stepping circuit, whereupon the stepping magnet cannot again be energized while relay 34 is opereted. The operation of relay 34 also closes its right-hand and middle contacts, thereby connecting the two sides of extension line B to the trunk circuit A.

The central ofiice operator is now signaled in any desired manner, and after conversation between the subscriber on extension line B and the subscriber connected with the other end of trunk circuit A is completed, the restoration of the receiver to the switchhook by the subscriber on extension line B causes the release of starting relay 30 and individual relay 31. The relay 31, in releasing, causes the release of relay 34, whereupon the extension line is disconnected from the trunk circuit and the operating circuit for stepping magnet 19 is completed from the battery, through the contact of relay 32, normal contact of relay 34, resistance 35 and the winding of stepping magnet 19 to ground. Stepping magnet 19 thereupon operates intermittently as long as relay 32 is energized, and since relay 32 is operated as long as the brush 16 is in engagement with contact ring 20, the ratchet wheel 10 and the brushes carried thereby will be rotated until in the normal position with the brush 16 out of engagement with ring 20.

Upon the switch reaching normal position, relay 32 and stepping magnet 19 release, whereupon all apparatus is returned to its tendant at the switchboard of the private branch exchange.

That is claimed is:

1. A telephone exchange system comprising a plurality of telephone lines normally terminating at a switchboard, a trunk circuit extending from this switchboard to a second switchboard, means at the first switchboard "for completing connection between any of the telephone lines and the trunk circuit, a line finding switch at the first switchboard, a manually controlled switch in each telephone line adapted, when actuated, to connect the lines with terminals of the finder switch, apparatus responsive to the removal of the receiver from the switch-hook at a calling station to start and continue the operation of'the line finding switch until the calling line is found, and apparatus responsive to the finding of the calling line for stopping the switch and for connecting the trunk circuit to the calling line.

2. A telephone exchange system comprising a plurality of telephone lines normally terminating at a switchboard, a trunk circuit extending from this switchboard to a second switchboard, means at the first switchboard for completing connection between any of the telephone lines and the trunk circuit, a step-by-step line finding switch at the first switchboard, a manually controlled key in each telephone line adapted, when actuated, to connect the line with terminals of the line finding switch, apparatus responsive tothe removal of the receiver from the switchhook at a station on one of the lines to start and continue the operation of the line finding switch until the calling lineis found, and apparatus responsive to the finding of the calling line for connecting the trunk circuit thereto.

trunk circuit, a step-by-step line finding switch at the first board, a manually con-' trolled key ineach telephone line adapted, when actuated, to connect the line with terminals of the line finding switch, apparatus responsive to the removal of the receiver from the switchhook at a station on one of the lines to start and continue the operation of the switch until the calling line is found, apparatus responsive to the finding of the calling line to stop the switch and connect the trunk circuit to the calling line, and apparatus actuated upon the starting of the switch serving when the receiver at the calling line is restored to the switchhook to again start the switch and continue the operation thereof until the normal position is reached.

4. A. telephone exchange system comprising a plurality of telephone lines normally terminating at a switchboard, a trunk circuit extending from this switchboard to a second switchboard, operator controlled means at the first switchboard for completing connection between any of the telephone lines and the trunk circuit, an automatic switching device associated with the first switchboard and normally disconnected from the telephone lines, operator controlled switching devices adapted when actuated to connect the automatic switching device with the telephone lines, and means operating upon the removal of the receiver from the switchhook at a calling station to cause the automatic switching device to connect the calling telephone line with the trunk circuit.

5. A telephone exchange system comprising a plurality of telephone lines normally terminating at a switchboard, a trunk circuit extending from this switchboard to a second switchboard, operator controlled means at the first switchboard for completing connection between any of the telephone lines and the trunk circuit, automatic switching mechanism associated with the first switchboard and normally disconnected from the telephone lines, operator controlled switching devices adapted when actuated to connect the telephone lines with the automatic switching mechanism, and a relay responsive to the removal of the receiver from the switchhook at a calling station to render the switching mechanism etfective for establishing connection between the calling telephone line and the trunk circuit.

In witness whereof, I hereunto subscribe my name this 4th day of November, A. D. 1916.

ROY E. NOBLE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). 0. 

